India Lightning Risk Map — IS 2309

Average annual thunderstorm days per IMD long-period (1971-2020) records. Drives the IS 2309:1989 Lightning Protection System (LPS) requirement — protection level, rolling-sphere radius, mesh size, down-conductor spacing, and earth resistance limit.
25
low
125
moderate
34
high
13
very-high
Low · < 30 thunderstorm days/year · < 30 t-days
Moderate · 30–50 t-days/year · 30–50 t-days
High · 50–80 t-days/year · 50–80 t-days
Very High · > 80 t-days/year · > 80 t-days
Loading map…
📍
Click anywhere on the map, or search a city
Try
Click any spot on the map to drop a pin and get the estimated zone. Map data © OpenStreetMap contributors.

About lightning protection

India records ~2,500 lightning deaths/year — among the highest globally. IS 2309 Cl. 7 risk-index R determines whether LPS is needed.R = N × A × C where N = annual flash density, A = collection area, C = consequence factor. R > 10⁻⁵ = LPS required.

Protection levels per IS 2309

  • Level I (highest, very-high zones): rolling sphere R = 20 m, mesh 5×5 m, down conductors at 10 m, earth ≤ 5 Ω.
  • Level II (high zones): R = 30 m, mesh 10×10 m, conductors 10 m, earth ≤ 10 Ω.
  • Level III (moderate zones): R = 45 m, mesh 15×15 m, conductors 15 m, earth ≤ 10 Ω.
  • Level IV (low zones, optional): R = 60 m, mesh 20×20 m, only for tall isolated structures.

Cross-references

Source IS / IRC / NBC standards

IS 2309:1989Lightning Protection of BuildingsNBC 2016 Part 8Lift + escalator earthing requirements

Related maps

Climate ZonesWarm-humid zones often = high thunderstormWind SpeedTall structures need both LPS + wind design

Calculators & tools

Cost CalculatorLPS adds ₹50K-1.5L per building

Articles & guides

CE HandbookEarthing + electrical safety reference

Frequently asked questions

Is lightning protection mandatory?

Per IS 2309 Cl. 7 + NBC 2016 Part 8: mandatory for buildings > 25 m, isolated structures (telecom towers, water tanks), critical occupancies (hospitals, schools, fuel storage), and for any structure in Very High thunderstorm-day zone (NE India, Bengal interior). Most state building bye-laws also require it for buildings > 15 m.

How much does an LPS cost?

₹50,000-1,50,000 for residential (G+3) up to 10-storey commercial. Per-floor: ₹15,000-25,000. Includes air terminals, down conductors (PVC-insulated 50 mm² Cu or 70 mm² GI), earth pits (3-4 typical), surge protection at electrical entries. Annual maintenance ₹5,000-15,000 (continuity + earth resistance test).

What earth resistance is required for LPS?

IS 2309 Cl. 12: ≤ 10 Ω for protection levels III-IV; ≤ 5 Ω for I-II. Achieved via 3-4 chemical earth pits in parallel, or earth mat + pits combination. Soil resistivity matters — sandy / rocky soils need more pits or chemical earth enhancers. Annual continuity + earth-resistance test mandatory.

Thunderstorm-day classification is from IMD long-period averages. Local terrain (hilltops, isolated structures, metallic chimneys) elevates risk regardless of regional zone. Always conduct IS 2309 Annex risk-index calculation for project-specific LPS sizing.

← Back to all engineering maps